feat(notifications): Add "Recording Stopped" notification on implied stop

[jan-law]

Fixes #781

[jan-law]

The latest CI build failure looks like #666 again:

Feb 04, 2022 6:19:57 PM io.cryostat.core.log.Logger info
INFO: io.cryostat.net.reports.SubprocessReportGenerator processing report
java.util.concurrent.ExecutionException: java.lang.NullPointerException
	at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
	at io.cryostat.net.reports.SubprocessReportGenerator.generateReportFromFile(SubprocessReportGenerator.java:336)
	at io.cryostat.net.reports.SubprocessReportGenerator.main(SubprocessReportGenerator.java:292)
Caused by: java.lang.NullPointerException
	at org.openjdk.jmc.flightrecorder.parser.synthetic.SyntheticAttributeExtension$ModuleExportSink.addEvent(SyntheticAttributeExtension.java:206)
...
Feb 04, 2022 6:19:57 PM io.cryostat.core.log.Logger error
SEVERE: HTTP 500: Internal Server Error
io.cryostat.net.web.http.api.v2.ApiException: Internal Server Error
Caused by: java.util.concurrent.ExecutionException: io.cryostat.net.reports.SubprocessReportGenerator$SubprocessReportGenerationException: [6] An unspecified unexpected exception occurred.
	at java.base/java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:395)
	at java.base/java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2022)
...
Feb 04, 2022 6:19:57 PM io.cryostat.core.log.Logger info
INFO: (10.0.2.100:53658): GET /api/beta/targets/service:jmx:rmi:%2F%2F%2Fjndi%2Frmi:%2F%2Fcryostat-itests:9091%2Fjmxrmi/reports/ReportJwtDownloadIT 500 981ms

[andrewazores]

The expected happy-path workflow seems to be working well, just those last two kinda corner cases above left. This will go nicely with cryostatio/cryostat-web#368 too - the active recordings table will update running recordings to the stopped state automatically, even without view refresh enabled.